1. Field of the Invention
This particular invention generally pertains to a system and method of substantially maintaining steady state conditions in a froth flotation operation. Specifically, the present invention is directed to a novel and improved method and system which continuously monitors the mass flow of the aqueous pulp of flotation concentrates which substantially continuously overflows from the flotation cell, whereby such monitoring results in the varying rate of admission of aeration air into the flotation cell, in a manner which is inversely proportional with respect to the variations in the mass flow of the concentrates to maintain steady state conditions which optimize the metallurgical output.
2. Description of the Prior Art
In the mining industry and, more particularly, in the field of froth flotation separation it is highly desirable to optimize the metallurgical output for such process. Difficulties, however, are experienced in attempting to provide and maintain such optimization since there are numerous variables which continually change during the normal and customary froth flotation process. As a result such process is in a state of disequilibrium wherein the continuity of flow of concentrates from each flotation cell is interrupted. Accordingly, an accurate control of such process is virtually extremely difficult to attain.
In actual field practice of the flotation process one of the more noteworthy causes for interruption of steady state operations are slight changes in ore characteristics, thereby requiring either more or less frother. Further, examples of additional factors affecting steady state conditions which have a tendency to diminish the metallurgical output of the flotation process are changes in water pressure, intermittent surging of flotation feed pulp, automatic or manual changes in grinding circuit, water additions to correct densities in the grinding mills, increased or decreased flow from pumps within the benefication system, changes in rougher concentrate density as a result of changes in flotation cell temperature, changes in blower pressure which serve to supply air to the flotation cells.
Heretofore, it has been a customary approach in this particular field to have a rougher flotation operator attempt corrective efforts in order to minimize the adverse effects of such process variations. In a conventional unit, for example, assuming flotation cells begin to "overfroth", the corresponding pulp levels would have to be lowered and/or air to such flotation cells reduced. On the other hand, if the benefication circuit has slowed down then the pulp levels would have to be correspondingly raised to achieve stabilization.
As is often the situation in practice, such stabilization period may be only for a very brief time interval since, as aforementioned, other process variables tend to upset the stabilization. Accordingly, the necessary stabilization adjustments would have to be continually repeated to achieve the desired steady state flow necessary for optimization of the froth flotation process.
A significant additional drawback, of course, to the above mentioned prior art shortcomings in attempting to control the process by correcting for variables to maintain equilibrium is the fact that valuable recoverable materials, such as copper and molybdenum are lost since they go to the final tailing. Such loss of minerals is, of course, economically undesirable.
As is believed rather evident from the foregoing description manual adjustments are rather limited. Moreover, for a manual operation to provide any meaningful effect to minimize the disruptive effects of the numerous variations occurring in the typical froth flotation process, such type of control would necessitate the employment of an excessive number of operators. This approach is, of course, commercially prohibitive in view of the rather significant time and labor costs involved, as well as the lack of complete continuity in providing for corrections to the variables, which tend to upset the desired or optimum operating conditions for the froth flotation operation. Additionally, the rather erratic and unpredictable occurrences of such disruptive factors in the process upset the stabilization of the entire ore benefication system.
In addition to the enumerated shortcomings generally associated with the manual approach in correcting the variances which tend to disrupt the desired operation of froth flotation process, there exist several other drawbacks. In the field, for instance, it has been determined that manual operators in attempting to achieve the desired stabilization often tend to overcompensate. Such overcompensation or adjustment by an operator will, of course, also tend to cause further disruptions or surges in the entire system thereby even further compounding the disruptions to steady state conditions resulting from the initial variance attempted to be controlled. Consequently, an efficient and reliable operation is virtually commercially impossible to successfully achieve with manual monitoring alone. As is evident such a control system significantly lacks the ability to maintain an accurate degree of high metallurgical recovery.
Several known methods have been proposed to alleviate the rather significant drawbacks generally associated with the manual control of froth flotation processes.
By way of specific example, one known approach for monitoring the froth flotation in a benefication process is described in U.S. Pat. No. 3,834,529 to Hart. This particular patent describes a somewhat complicated system for controlling the froth flotation, wherein the density of mineral slurry at selected stages in a flotation system is continuously monitored whereby the differentials in density of the slurry serve to provide control signals. In turn, the control signals permit adjustment of, for example, feed compositions. Beyond being rather complicated, the system does not provide for as quick and simple adjustment as could otherwise be desired.
Other known approaches to improve upon the efficiency of a flotation benefication process include, for instance, adjusting the pulp density in the lower portion of a flotation cell and by controlling the rate of tailing withdrawal through an outlet conduit. Another conventional unit employs a relatively small sampling vessel which continuously senses the quantity of froth overflow to control the liquid level within the froth flotation cell by appropriately raising and lowering a tailings gate in response to pressure differentials. Moreover, any effort to control the pulp level with a monitoring system is known industrial rougher flotation cells would be rather complicated and cumbersome to install, given the configuration of conventional rougher flotation circuits. For example, four level controls would have to be put on each bank of cells. Such arrangement, therefore, would involve twenty-four level controls in a standard industrial arrangement. Quite obviously, such an approach beyond being complicated and expensive would also be subject to an increased likelihood of maintenance and repair costs.
Still another conventional system particularly adapted for use in controlling froth flotation operations essentially employs an instantaneous radiation assaying unit for assaying one of the elemental content of a flotation pulp sample.
Although numerous kinds of systems and methods exist for optimizing the froth flotation system they are, in general, relatively complicated in structure and operation not to mention fail to generally provide for a system which simply, yet reliably provides for a continuous and automatic control of the froth flotation process which provides for improved metallurgical tonnage recovery.